Automated extended depth of field imaging apparatus and method

ABSTRACT

An imaging apparatus and method enables an automated extended depth of field capability that automates and simplifies the process of creating extended depth of field images. An embodiment automates the acquisition of an image “stack” or sequence and stores metadata at the time of image acquisition that facilitates production of a composite image having an extended depth of field from at least a portion of the images in the acquired sequence. An embodiment allows a user to specify, either at the time of image capture or at the time the composite image is created, a range of distances that the user wishes to have in focus within the composite image. An embodiment provides an on-board capability to produce a composite, extended depth of field image from the image stack. One embodiment allows the user to import the image stack into an image-processing software application that produces the composite image.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.14/570,594, filed on 15 Dec. 2014, which is a continuation of U.S.application Ser. No. 13/420,434, filed on 14 Mar. 2012, which was issuedas U.S. Pat. No. 8,913,174 on 16 Dec. 2014, which is a continuation ofU.S. application Ser. No. 12/398,034, filed 4 Mar. 2009, which wasissued as U.S. Pat. No. 8,154,647 on 10 Apr. 2012, which claims priorityto U.S. Provisional Application No. 61/034,088, filed 5 Mar. 2008, eachof which is incorporated herein in its entirety by this referencethereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In general the invention relates to extending the depth of field inimages. More particularly, the invention relates to an imagingapparatus, having an automated extended depth of field mode, andassociated method.

2. Background Information

Obtaining sufficient depth of field is a constant challenge inphotography, particularly when photographing at extremely close range orunder low lighting conditions. Setting the lens to a small apertureyields more depth of field, but this technique is eventually limited bydiffraction effects and may mandate excessively long exposure times. Thetraditional approach to this difficulty required the photographer to“determine the optimum lens aperture for effecting the golden meanbetween stopping down the lens for depth of field and opening it up forgood resolution”. Close-up Photography & Photomacrography 78 (KodakTechnical Publication N-12, Eastman Kodak Co. 1977).

However, advances in image post-processing have enabled a new approachto this challenge. In extended depth of field (EDOF) photography, aphotographer captures a “stack” of images, sweeping the focus distanceof the lens through the range of interest in a stepwise fashion.Post-processing software then combines the stack images into a singlecomposite image by selecting from each stack image the in-focus portionof the image. The resulting composite image thus provides both highresolution and a large depth of field. However, this technique requiresthe photographer to determine the depth of field provided by the lensand aperture, and to then manually advance the focus distance of thelens by the appropriate amount between acquisition of each stack image.This is both tedious and prone to error.

Software control programs are available that control camera systems toproduce image stacks, wherein each image is taken at different focuspoints within the subject. However, the software programs run externallyto the imaging apparatus, therefore requiring a separate computingapparatus, communicatively coupled to the imaging apparatus forexecuting the control software. Additionally, the task of mastering suchcontrol programs may be difficult and time-consuming. Furthermore, suchprograms are not widely available, typically being provided bymanufacturers or VAR's (value-added resellers) for specific imagingapparatus.

Digital cameras having an automated focus bracketing feature are nowavailable. In photography, “bracketing” is the general technique oftaking several shots of the same subject using different camerasettings. A camera having an automated focus bracketing capability takesa series of shots of a subject, automatically changing the focaldistance after each shot. Typically, the photographer may choose from anumber of settings that specify the number of shots. Such bracketingfeatures do not embody automated intelligence for calculating thespacing of images in a stack for (EDOF) photography based onphotographer-selected near and far focus limits.

SUMMARY

An imaging apparatus and method automates and simplifies the process ofcreating extended depth of field images. An embodiment automates theacquisition of an image stack and stores metadata at the time of imageacquisition that facilitates production of a composite image having anextended depth of field from at least a portion of the images in theacquired stack. An embodiment allows a user to specify, either at thetime of image capture or at the time the composite image is created, arange of distances that the user wishes to have in focus within thecomposite image. An embodiment provides an on-board capability toproduce a composite, extended depth of field image from the image stack.An embodiment allows the user to import the image stack into animage-processing software application that produces the composite image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a block diagram of a digital camera having an automated,extended depth-of-field mode;

FIG. 2 provides a flow diagram of a method for acquiring a stack ofimages having depths of field that span a predetermined distance rangefor production of extended depth-of-field (EDOF) images;

FIG. 3 provides a flow diagram of an alternate embodiment of a methodfor acquiring a stack of images having depths of field that span apredetermined distance range for production of EDOF images.

DETAILED DESCRIPTION

An imaging apparatus and method automates and simplifies the process ofcreating extended depth of field images. An embodiment automates theacquisition of an image stack and stores metadata at the time of imageacquisition that facilitates production of a composite image having anextended depth of field from at least a portion of the images in theacquired stack. An embodiment allows a user to specify, either at thetime of image capture or at the time the composite image is created, arange of distances that the user wishes to have in focus within thecomposite image. An embodiment provides an on-board capability toproduce a composite, extended depth of field image from the image stack.An embodiment allows the user to import the image stack into animage-processing software application that produces the composite image.

FIG. 1 shows a diagrammatic representation of a digital camera 100having an automated extended depth-of-field (EDOF) mode, according tothe invention.

The digital camera 100 includes a housing 102, a lens shutterarrangement system 104 having a focusable lens 106 and a shutter 108,and an image-sensing device 110, such as a CCD (charge-coupled device).One embodiment may include a camera setting adjustment system 114. Thecamera setting adjustment system 114 may include a stepper motor 112 forincrementally adjusting the focus distance of the lens 106 and the sizeof the aperture opening. Additionally, the camera setting adjustmentsystem may include an embedded system 116, the embedded system includingat least one processor and a motor driver for facilitating incrementalchanges in focus distance and aperture via the stepper motor 112.

In one embodiment, the digital camera may include both fixed focus andauto-focus modes. Selection of focus mode may be accomplished by meansof a switch (not shown) or by activating a focus mode-selectioncomponent in a user interface displayed on the LCD display 120. As shownin FIG. 1, the display is communicatively coupled to the embedded system116 by means of leads 122.

An embodiment allows the user to specify the range of distances at thetime of image capture. This may be done manually, for example, byselecting the defining distances via a pair of manual dials (not shown)or by selecting numerical values defining the range on the LCD display120, or in a camera-assisted manner by using the camera's autofocusfeature to specify the near and far limits of the range; for example bypointing a spot-metering range finder (within the auto-focus system ofthe camera) at two or more points of interest. Additional embodimentsmay employ, for example, weighted average metering or forms ofobject-class detection such as face detection to specify near and farlimits of the range. The camera then acquires a stack of images atspaced intervals sufficient to provide in-focus coverage across thedesired range, wherein the processor of the embedded system isprogrammed to control the process of acquiring an image stack forcreation of one or more EDOF images.

The foregoing description of an image capture apparatus is meant only tobe illustrative and is not intended to be limiting. In light of thepresent description, the ordinarily-skilled practitioner will understandthat other types of programmable image capture devices, for example,programmable film cameras, are entirely suitable for producing EDOFimages by the process described herein.

As above, the embedded system 116 includes at least one processor.Additionally, the embedded system includes a read-only memory havingstored therein one or more firmware modules for programming the at leastone processor to execute the steps of a process for producing EDOFimages as described herein.

In one embodiment, the embedded system may be composed of an ASIC(application specific integrated circuit) or one or more CMOSs(complementary metal oxide semiconductors). In other embodiments, thelogic component of the embedded system may be a microcontrollerprogrammed as below, or a FPGA (field programmable gate array) havinglogic circuits for performing the steps of the procedure below.

Referring now to FIG. 2, acquisition of the image stack begins with thecamera first approximating 202 the hyperfocal distance H:

$\begin{matrix}{H \approx \frac{f^{2}}{Nc}} & (1)\end{matrix}$

based on the f-number, N, the lens focal length, f, and the maximumpermissible circle of confusion c. The practitioner of ordinary skillwill appreciate that, in the fields of optics and photography,hyperfocal distance is the closest distance at which the lens can befocused while keeping objects at infinity acceptably sharp. Theordinarily-skilled practitioner will understand that the maximumpermissible circle of confusion is the largest circle of confusionconsidered to provide acceptably sharp focus.

Then, beginning at one end of the specified range of distances, thefocus distances, s_(i), for the stack images are computed iterativelybased on approximations for the near and far limits—D^(n) and D^(f),respectively—of the depth of field:

$\begin{matrix}{{D^{n} \approx \frac{Hs}{H + s}}{and}} & (2) \\{D^{f} \approx {\frac{Hs}{H - s}.}} & (3)\end{matrix}$

For example, beginning at the far end of the specified range ofdistances, r^(f), the initial focus distance is computed by solving forthe focus distance in Equation 3 with D^(f)=r^(f). That is,

$\begin{matrix}{s_{1} = {\frac{{Hr}^{f}}{H + r^{f\;}}.}} & (4)\end{matrix}$

Then, the corresponding near depth of field limit is found usingEquation 2, namely:

$\begin{matrix}{D_{1}^{n} = {\frac{{Hs}_{1}}{H + s_{1}}.}} & (5)\end{matrix}$

The procedure is repeated with the near depth of field limit applied asthe far limit of the depth of field in the next iteration. Specifically,

$\begin{matrix}{s_{i} = \frac{{HD}_{i - 1}^{n}}{H + D_{i - 1}^{n}}} & (6) \\{{D_{i}^{n} = \frac{{Hs}_{i}}{H + s_{i}}},} & (7)\end{matrix}$

with D₀ ^(n)=r^(f). Substituting, the procedure can be summarized as

$\begin{matrix}{s_{1} = \frac{{Hr}^{f}}{H + r^{f}}} & (8) \\{s_{i} = {\frac{{Hs}_{i - 1}}{H + {2s_{{i - 1}\;}}}.}} & (9)\end{matrix}$

The iterative procedure continues until the near depth of field limit iswithin the near end of the specified range of distances. That is,iteration proceeds 204 until iteration N when D_(N) ^(n)≦r^(n).Equivalently, this occurs when

$\begin{matrix}{s_{N} \leq {\frac{{Hr}^{n}}{H - r^{n}}.}} & (10)\end{matrix}$

The result of the procedure is a stack of N images having abuttingdepths of field, covering the specified range of distances.

Of course, it is unlikely that the final image will be at a focusdistance, s_(N), with a near depth of field limit, D_(N) ^(n),corresponding to the near end of the specified range of distances,r^(n). Most likely, the final image will provide in-focus content nearerthan r^(n). An embodiment therefore preferably allows the user tospecify whether he desires to have “at least” the specified range ofdistances in focus or “exactly” the specified range of distances infocus. Based on this specification 206, the final focus distance may beadjusted. In the former case, no adjustments need be made to the finalfocus distance. The result is a set of focus distances for a stack ofimages covering at least the specified range of distances. Based on thisset of focus distances, the camera then obtains 208 a stack of N imageshaving abutting depths of field, covering at least the specified rangeof distances. In the latter case, the final focus distance is adjustedsuch that the near depth of field limit corresponds to the near end ofthe specified range of distances 210, that is,

$\begin{matrix}{s_{N^{\prime}} = {\frac{{Hr}^{n}}{H - r^{n}}.}} & (11)\end{matrix}$

The result is a set of focus distances for a stack of images havingabutting depths of field covering exactly the specified range ofdistances. Based on this set of focus distances, the camera then obtains212 a stack of N images having abutting depths of field, coveringexactly the specified range of distances.

Alternatively, the images within the image stack may be acquired aftereach focus distance is calculated. In this embodiment, the adjustmentstep at block 210 may be performed by acquiring an additional image toreplace the final image of the stack already acquired.

EXAMPLE I

An exemplary calculation of focus distances according to the aboveprocedure proceeds as follows:

A photographer operating a camera and f=35 mm lens at N=4.0 specifies arange of distances r^(n)=5 m and r^(f)=25 m. The camera images using aCCD sensor characterized by a circle of confusion of c=6 μm. Then, fromEquation 1, H=51.04 m. Iterating according to Equations 8 and 9, thefocus distances are determined to be s₁=16.78 m, s₂=10.12 m, s₃=7.25 m,s₄=5.65 m and s₅=4.62 m. Iteration ceases in accordance with Equation 10with s₅≦5.54 m. As noted above, the final focus distance, s₅, mayoptionally be adjusted according to Equation 11 to s_(5′)=S_(N′)=5.54 m.

Alternatively, as shown in FIG. 3, it is possible to begin with the nearend of the specified range of distances. In this approach, the procedurecan be summarized as

$\begin{matrix}{s_{1} = \frac{{Hr}^{n}}{H - r^{n}}} & (12) \\{{s_{i} = \frac{{Hs}_{i - 1}}{H - {2s_{i - 1}}}},} & (13)\end{matrix}$

with termination upon

$\begin{matrix}{{s_{N} \geq \frac{{Hr}^{f}}{H + r^{f}}},} & (14)\end{matrix}$

and optional adjustment of the final image to

$\begin{matrix}{{s_{N^{\prime}} = \frac{{Hr}^{f}}{H + r^{f}}},} & (15)\end{matrix}$

as previously described with respect to FIG. 1. If the user does notspecify that the range of distances needs to be exact 306, the cameraobtains 308 a stack of images covering at least the specified rangeresults. If the user specifies that the range must be exact 306, thefocus distance of the final image is adjusted 310 so that the far depthof field limit corresponds to far end of the specified range ofdistances, and the camera obtains 312 a stack of images covering exactlythe specified range.

As with the process of FIG. 2, in an alternative embodiment, the imageswithin the image stack may be acquired after each focus distance iscalculated, and the adjustment step at block 310 may be performed byacquiring an additional image to replace the final image of the stackalready acquired.

EXAMPLE II

Again using the exemplary values of f=35 mm, N=4.0, r^(n)=5 m andr^(f)=25 m, and c=6 μm, and iterating according to Equations 12 and 13,the focus distances are determined to be s₁=5.54 m, s₂=7.08 m, s₃=9.80m, s₄=15.91 m, and s₅=42.24 m. Iteration ceases in accordance withEquation 14 with s₅≧16.78 m, and the final focus distance may optionallybe adjusted according to Equation 15 to s_(5′)=S_(N′)=16.78 m.

It is worth noting that the above procedures do allow the user tospecify a range of distances in which r^(f)=∞. In this case, in theinwardly-iterating procedure, the initial image is acquired at thehyperfocal distance. In the outwardly-iterating procedure, iteration isterminated when the focus distance exceeds the hyperfocal distance, andthe focus distance of the final image is optionally adjusted back to thehyperfocal distance.

The procedures—in particular, the termination criterion in the inwardlyiterating procedure and the initial image focus distance in theoutwardly iterating procedure—do become indeterminate should a userspecify a range of distances in which r^(n)>H. Such situations may behandled as special cases. For example, if the user requests that “atleast” the specified range of distance be in focus, the camera canacquire a single image at a focus distance s=H. If the user requeststhat “exactly” the specified range of distance be in focus, a warningmay be presented to the user prior to acquisition of a single image ats=H.

As can be seen, both the number and spacing of the stack images aredependent on the f-number N. Preferably, the f-number is determinedautomatically by the camera using existing methods that consider, forexample, the capabilities of the lens and the light level. However, theinvention can also be used in conjunction with an “aperture priority”mode in which the user may specify a specific f-number at which thestack images are to be acquired. For example, a user willing to toleratereduced sharpness in the composite image could reduce the number ofstack images required by specifying a relatively small f-number. Thesystem may also allow the user to specify specific f-numbers for theindividual stack images, thus allowing customization of the stack imagespacing.

Similarly, the number and spacing of stack images is dependent on themaximum permissible circle of confusion c. Preferably, the value of c isselected automatically by the camera, based on the inherent limitations(i.e., the optical quality) of the lens, the capabilities (i.e., theresolution) of the imaging format (e.g. 35 mm film, CCD), and the amountof diffraction associated with the chosen f-number. Alternatively, thecircle of confusion may be specified by the user as desired. Forexample, a user willing to tolerate reduced sharpness in the compositeimage in order to reduce the number of stack images required couldspecify a relatively large maximum permissible circle of confusion.

In yet a further embodiment, the user can specify an “overlap fraction”,a of adjacent depths of field in the image stack. As in previousembodiments, hyperfocal distance and focus distances are calculated. Inthis case, however, the user specifies an overlap fraction. In thiscase, the procedures described herein above are modified such that thefocus distance of each image within the image stack is adjusted to placeone depth of field limit within the previous depth of field. Forexample, in the inwardly-iterating procedure, the focus distance(Equation 6) is adjusted to

$\begin{matrix}{s_{i} = \frac{{HD}_{i}^{f}}{H + D_{i}^{f}}} & (16)\end{matrix}$

where the far depth of field limit is within the previous depth of fieldas specified by α, namely,

D _(i) ^(f) =D _(i-1) ^(n)α(D _(i-1) ^(n) −D _(i-1) ^(n)).  (17)

Application of the overlap fraction results in a stack of images havingoverlapping depths of field. In the absence of an overlap fraction, astack of images having abutting depths of field results.

EXAMPLE III

Returning to the example above, with an overlap fraction of α=0.2,Equations 16 and 17 yield focus distances of s₁=16.78 m, s₂=11.65 m,s₃=8.78 m, s₄=7.00 m, s₅=5.81 m, and s₆=4.95 m and depths of field [D₁^(n), D₁ ^(f)]=[12.63 m, 25.00 m], [D₂ ^(n), D₂ ^(f)]=[9.49 m, 15.10 m],[D₃ ^(n), D₃ ^(f)]=[7.49 m, 10.61 m], [D₄ ^(n), D₄ ^(f)]=[6.16 m, 8.12m], [D₅ ^(n), D₅ ^(f)]=[5.21 m, 6.55 m], and [D₆ ^(n), D₆ ^(f)]=[4.51 m,5.48 m].

A still further embodiment extends to multiple ranges of distance thatthe user wishes to have in focus. In this embodiment, each range can behandled separately, as described above.

In yet another embodiment, the user can specify one or more ranges ofdistances that he wishes to be out of focus. In this case, the out offocus ranges can be converted to one or more complementary in focusranges, each handled as described above.

Finally, in yet another embodiment, the camera automatically acquires astack of images providing coverage from the near field to infinity at anextremely small f-number. Because each image within the stack offers alimited depth of field, it is then possible for the photographer toselect, in post-processing software, what distances he would like tohave in focus and what regions he would like to have out of focus. Basedon the metadata saved by the camera for each image within the stack, thepost-processing software assembles the composite image from theappropriate images within the stack. This approach does require thecapture and storage of more stack images than may ultimately beutilized, but it does provide the photographer with greater artisticfreedom later in the production process.

Finally, the ordinarily-skilled practitioner will appreciate that theexpression in Equation 1 is only one possible approximation of thehyperfocal distance, and the expressions of Equations 2 and 3 are onlytwo possible approximations of the limits of the depth of field. Inparticular, these approximations are valid only for relatively largefocus distances in which s>>f. Especially in the case of extremely closesubject matter—such as in macrophotography—the depth of field may becalculated by any number of well known alternative approximations, anddifferent approximations may be used at different focus distances—inother words, different images within the stack.

The above procedures are preferably invoked by the user via selection ofan “auto-EDOF mode”, analogous to “shutter priority” or “program” modesfound on many cameras. For example, the user may select the mode on arotary dial atop the camera. After selection of the mode andspecification of the range of distances, the stack of images ispreferably acquired as rapidly as possible in response to a single pressof the shutter button. In the case of an SLR (single lens reflex)camera, the reflex mirror may be held in a retracted position while theimages are acquired. In the case of a digital camera, the images may bewritten to a temporary memory cache offering faster write times than thepermanent memory, enabling faster image acquisition. Nonetheless, as thestack images are still acquired over a span of time, the invention maybe combined with any of several well-known techniques for digital imagestabilization that are capable of backing out any motion of the subjector camera that occurs between successive images within the stack; forexample the “image stack” feature within PHOTOSHOP (ADOBE SYSTEMS, INC.,San Jose, Calif.) or such image-processing software as HELICON FOCUS(HELICON SOFTWARE, LTD., Kharkov, Ukraine).

As noted above, the stack of images is combined into a single compositeimage during post-acquisition processing. In one embodiment, theprocessing is performed off-board the camera by a computational deviceprogrammed with an image processing software application for creatingextended depth of field images. Examples of such software applicationare COMBINEZ5 and COMBINEZM, both open-source programs obtainable on theInternet, and both originally developed by Alan Hadley, a resident ofthe United Kingdom. To better facilitate post-processing operations, thecamera saves metadata with each image in the stack, preferablyindicating the inner and outer boundaries of the depth of field for theimage and the specified range of distances. At a minimum, the camerastores information from which these quantities can be determined, forexample the f-number, the lens focal length, and the maximum possiblecircle of confusion. The information is preferably stored in astandardized set of meta-data tags, such as those within theexchangeable image file format (EXIF).

In a further embodiment, the images may be combined into a singlecomposite image onboard the camera. In this case, the stack images maybe deleted after composition to increase available memory space.

The methods and systems herein described provide a large number ofunexpected benefits which render them a great advance over theconventional manner of producing extended depth of field images. Theforemost advantage provided by present methods and systems is that theyprovide an integrated solution to the challenge of producing extendeddepth of field (EDOF) images. Presently, practitioners in this art mustfirst acquire the images, largely, manually. The practitioner determinesthe depth of field boundaries and the corresponding depths of field atwhich it is necessary to acquire images in order to cover the desiredrange of distances. After acquiring the image stack, the practitionermust then export the image stack to a third-party software applicationwith which the composite, extended depth of field image is created.

The integrated solution provided by the present systems and methodsgreatly increases the ease with which such images may be produced. Untilnow, EDOF image production presented a formidable technical challengerequiring a high level of skill in the operation of imaging equipment,the integrated solution described herein reduces the level of requiredtechnical skill to approximately that required to operate a digitalcamera.

The present solution greatly simplifies the step of defining the focusrange for the EDOF image, substituting a simple, intuitive procedurewhereby the user defines the focus range by tagging successive focuspoints using the autofocus feature of a digital camera for thecumbersome manual procedure now generally used.

The present solution also greatly simplifies the acquisition of theimage stack. The system intelligently calculates the required depths offield to cover the specified range of distances and automaticallyacquires the image stack, with little or no additional user input. Oneembodiment integrates the production of the EDOF image, eliminating theneed for yet another software application to produce the image, andgreatly reducing the storage and transfer bandwidth requirementsinvolved in EDOF image production.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

1. A method, comprising: receiving a range of distances external to animaging apparatus to be in focus for a composite, extendeddepth-of-field image; and acquiring a stack of images with the imagingapparatus, the acquired stack of images having depths of field coveringthe received range of distances.
 2. The method of claim 1, wherein thereceived range of distances is received from a user, either before orafter the acquiring the stack of images, either by: a directspecification by the user of the range of distances; or a specificationby the user of boundaries of an out-of-focus range of distances, whereinan inverse of the out-of-focus range of distances comprises the range ofdistances.
 3. The method of claim 1, wherein the received range ofdistances are specified by a user though a user interface.
 4. The methodof claim 1, wherein the imaging apparatus includes any of a digitalcamera or a film camera.
 5. The method of claim 1, further comprising:creating the composite, extended depth-of-field image from at least aportion of the stack of images.
 6. The method of claim 1, whereinacquiring the stack of images having depths of field covering thereceived range of distances comprises: iteratively computing a focusdistance for each stack image based on hyperfocal distance and near andfar limits of the received range of distances until at least thereceived range of distances is covered; and acquiring at least one imageat each computed focus distance.
 7. The method of claim 6, furthercomprising: inputting a user specification to have exactly the receivedrange of distances in focus.
 8. The method of claim 7, furthercomprising: automatically adjusting the focus distance of a terminalimage in the received range of distances so that a depth of field limitfor the terminal image corresponds to a specified limit of the receivedrange of distances.
 9. The method of claim 1, wherein the acquiring thestack of images is performed by a processor upon activation of a controlelement.
 10. A device, comprising: a user interface that enables receiptof a range of distances external to a imaging apparatus to be in focusfor a composite-depth-of-field image; and a processor that includesinstructions to acquire a stack of images with the imaging apparatus,the stack of images having depths of field covering the received rangeof distances.
 11. The device of claim 10, wherein the received range ofdistances is received from a user, either before or after acquisitionthe stack of images, either by: a direct specification by the user ofthe range of distances; or a specification by the user of boundaries ofan out-of-focus range of distances, wherein an inverse of theout-of-focus range of distances comprises the range of distances. 12.The device of claim 10, further comprising: a user interface forspecification by a user of the range of distances.
 13. The device ofclaim 10, wherein the imaging apparatus includes any of a digital cameraor a film camera.
 14. The device of claim 10, wherein the processorincludes instructions to create the composite, extended depth-of-fieldimage from at least a portion of the stack of images.
 15. The device ofclaim 10, wherein the instructions to acquire the stack of images havingdepths of field covering the received range of distances includes:instructions for the processor to iteratively compute a focus distancefor each stack image based on hyperfocal distance and near and farlimits of the received range of distances until at least the receivedrange of distances is covered; and instructions for the processor toacquire at least one image at each computed focus distance.
 16. Thedevice of claim 15, wherein the processor includes instructions forinputting a user specification to have exactly the received range ofdistances in focus.
 17. The device of claim 16, wherein the processorincludes instructions for adjusting the focus distance of a terminalimage in the received range of distances so that a depth of field limitfor the terminal image corresponds to a specified limit of the receivedrange of distances.
 18. A non-transitory computer readable mediumincluding instructions for performing, wherein executed by a processor,a method comprising: receiving a range of distances external to animaging apparatus to be in focus for a composite, extendeddepth-of-field image; and acquiring a stack of images with the imagingapparatus, the stack of images having depths of field covering thereceived range of distances.